1. Field of the Invention
The invention relates to methods for making thermal interface materials and, particularly, to a method for making a thermal interface material having carbon nanotube array.
2. Discussion of Related Art
Many electronic components such as semiconductor chips are becoming progressively smaller with each new product release, while at the same time the heat dissipation requirements of these kinds of components are increasing due to their improved ability to provide more functionality. Commonly, a thermal interface material is utilized between an electronic component and a heat sink in order to fill air spaces therebetween and thereby promote efficient heat transfer.
Carbon nanotubes (CNTs) produced by means of arc discharge between graphite rods were first discovered and reported in an article by Sumio Iijima, entitled “Helical Microtubules of Graphitic Carbon” (Nature, Vol. 354, Nov. 7, 1991, pp. 56-58). An another article authored by Savas Berber, entitled “Unusually High Thermal Conductivity of Carbon Nanotubes” (page 4613, Vol. 84, Physical Review Letters 2000) discloses that a heat conduction coefficient of a carbon nanotube can be 6600 W/mK (watts/milliKelvin) at room temperature. That tends to make CNTs ideal candidates for thermal interface material.
A method for making the thermal interface material having CNT array is by diffusing particles with a high heat conduction coefficient therein. The particles can be made of graphite, boron nitride, silicon oxide, alumina, silver, or other metals. However, the diffusing particles can not be uniformly dispersed into the CNT array, because of the interspaces therein is small, and interfaces between some diffusing particles and CNTs in the CNT array is high. Therefore, heat conduction coefficient of the thermal interface material is low and cannot adequately meet the heat dissipation requirements of modern electronic components.
Another method for making the thermal interface material having CNT array is by injection molding. In this method, the CNT array is filled with a polymer material. However, the thermal interface material formed by injection molding is relatively thick. This increases a bulk of the thermal interface material, reduces its flexibility. Furthermore, because of filled with the polymer material, the heat conducting efficiency of thermal interface material is low.
Therefore, a simple method for making a thermal interface material is desired, which is thin, flexible and has a high heat conducting efficiency.